1. Field of the Invention
The subject invention generally relates to a composition and a process for forming a flexible polyurethane foam sealing device. Specifically, the polyurethane foam sealing device is capable of withstanding increased temperatures within high performance engines.
2. Description of Related Art
The related art discloses compositions for forming flexible polyurethane foam sealing devices, such as gaskets. These compositions generally include an isocyanate component and a resin component. Various attempts have been made to produce sealing devices that could withstand increased temperatures.
One such related art sealing device is disclosed in U.S. Pat. No. 5,510,053 to Narayan et al. The '053 patent discloses an isocyanate prepolymer composition for use in forming the sealing device. Additionally, the '053 patent discloses using a polyether polyol having a functionality of from 1 to 4, which may include graft polyols, and a blowing agent that is comprised only principally of water. The composition produces sealing devices that have a compression set for 50% deflection of 1.3% at 158° F. for 22 hours to 23.8% at 180° F. for 22 hours (See Examples 2-5). Based upon these results, the sealing devices formed in accordance with the '053 patent cannot produce a satisfactory sealing device at temperatures in the range of 240-250° F.
Another related art sealing device is disclosed in U.S. Pat. No. 6,103,851 to Roser et al. The '851 patent discloses sealing devices formed from an elastomer for use at high temperatures. The sealing device is formed from a resin component having a polyol with a functionality of 3 or greater reacted with an isocyanate. The composition forms a polyurethane elastomer and does not include either a physical blowing agent or a chemical blowing agent. The '851 patent does not disclose any improved compression set properties of the sealing device.
As the vehicle industry continues to refine the performance of the engine, the engines operate under higher temperatures than ever before. Therefore, the sealing devices must be improved to withstand such temperatures. It is believed that these higher temperatures result from the engines being smaller and more compact while also improving engine efficiency.
The related art is characterized by one or more inadequacies. Specifically, the related art polyurethane foam sealing devices do not have satisfactory compression set properties at increased temperatures. These gaskets do not rebound after being subjected to the increased temperatures. This could lead to gasket failure and leaking within the engine. Additionally, when the engines are serviced, the compressed sealing device must be replaced to prevent premature failure of the sealing device.